This Program Project entitled "Signaling of Endothelial Permeability and Lung Vascular Injury" addresses signaling pathways mediating increased endothelial permeability and microvascular injury. The overall objective of the Program Project is to define the regulatory signaling pathways using multi-disciplinary strategies involving investigators from Departments of Pharmacology, Biological Chemistry, Anesthesiology, and Medicine. In Project 1, we will address signaling mechanisms of increased endothelial permeability involving transcytosis in endothelial cells. These studies will define regulation of this pathway and its functional significance in the pathophysiology of increased lung microvascular permeability. In Project 2, we will study regulation of nitric oxide (NO) oxide (NO) production by the recently cloned carboxypeptidases D and M localized in plasma membranes of monocyte/macrophage and endothelial cells. We will study the function of these regulatory enzymes in providing the arginine substrate for NO production and the autocrine and paracrine role of No in signaling the increase in endothelial permeability. In Project 3, we will study the interactions between the thrombin receptor (PAR-1) and other PARs and specific G-proteins to which they are coupled in endothelial cells. We will determine whether expression of sequence-specific peptides interfering with PAR-1-G protein signaling can prevent thrombin-activated increase in endothelial permeability and expression of endothelial adhesivity (via P-selectin and ICAM-1 expression). The three projects will be supported by three cores: Administrative, Cell Culture and Hybridoma and Biochemistry/Molecular Resources which will integrate the objectives of each project to the program's overall objective. The goal of addressing the signaling mechanisms regulatory pulmonary vascular endothelial permeability will assist in the development of novel strategies aimed at preventing microvessel injury in lungs.